Electronic injection-controlling system for internal combustion engines

ABSTRACT

The injection controlling circuit in an internal combustion engine of a known type comprising a flip-flop controlled by the rotation of the engine so as to generate at predetermined moments injection-controlling signals, in association with a circuit producing end-of-injection signals in accordance with the operative parameters of the engine, means are provided to terminate the injections whenever there is a too sudden modification in the admission of fuel to the engine. To this end, the acceleration pedal controls the slider of a potentiometric voltage divider and a sudden shifting of said slider charges a condenser which prevents operation of the flip-flop. This is accomplished for by the application of a pulse by the transiently charged condenser to the base of a transistor which is thus rendered conductive and which grounds the input of the flip-flop through its collector-emitter circuit connected between said input and ground.

United States Patent Monpetit June 27, 1972 [54] ELECTRONIC INJECTION-CONTROLLING SYSTEM FOR INTERNAL COMBUSTION ENGINES 211 App1.No.: 25,094

[52] U.S. C1 ..123/32 EA, 123/119R [51] Int. Cl ...F02b 3/00, F02b 33/00[58] Field of Search 123/32 E [56] References Cited UNITED STATESPATENTS 2,845,910 8/1958 Pribble ..123/32 3,578,116 5/1971 Nakajima......l23/97 B 3,590,793 7/1971 Masalti ...123/97 B 2,859,738 11/1958Campbell ...l23/32 E 2,911,966 11/1959 Pribble ...l23/32 E 2,936,7445/1960 Paule ...l23/32 E 2,981,246 4/1961 Woodward ..123/32 E 3,430,6163/1969 Glockler ..123/32 E 3,456,628 7/1969 Bassot ...l23/32 E 3,463,130Reichardt ..123 32 E 3,515,104 6/1970 Reichardt ..123/32 E FOREIGNPATENTS 0R APPLlCATlONS 1,243,288 12/1959 France t ..123/32 E 1,125,7189/1957 Germany.. ...l23/32 E 1,126,677 1/1960 Germany ..123/32 E PrimaryE.taminerLaurence M. Goodridge Assistant ExaminerRonald B. CoxAtt0rney1(enyon Kenyon Reilly Carr & Chapin ABSTRACT The injectioncontrolling circuit in an internal combustion engine of a known typecomprising a flip-flop controlled by the rotation of the engine so as togenerate at predetermined moments injection-controlling signals, inassociation with a cir-- cuit producing end-of-injection signals inaccordance with the operative parameters of the engine, means areprovided to terminate the injections whenever there is a too suddenmodification in the admission offuel to the engine. To this end, theacceleration pedal controls the slider of a potentiometric voltagedivider and a sudden shifting of said slider charges a condenser whichpreventsoperation of the flip-flop. This is accomplished for by theapplication of a pulse by the transiently charged condenser to the baseof a transistor which is thus rendered conductive and which grounds theinput of the flipflop through its collector-emitter circuit connectedbetween said input and ground.

1 Claim, 1 Drawing Figure PATENTEDJum 19m 3, 672,345

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ELECTRONIC INJECTION-CONTROLLING SYSTEM FOR INTERNAL COMBUSTION ENGINESThe present invention has for its object improvements in the electroniccontrol of the injection in internal combustion engines for automobilevehicles.

The advantages of an electronic control of the injection are well knownand various systems have already been proposed as prototypes or arealready on the market.

Most known systems utilize controlling flip-flop circuit triggered by asignal produced by a pulse generator in synchronism with the rotation ofthe engine and adapted to start the injection, the duration of injectionand consequently the amount of fuel injected being defined in accordancewith the conditions of operation of the engine by means of delay circuitforming part of the flip-flop circuit or constituting anindependent'unit.

Such control circuits provide means for incorporating a number of engineoperating parameters with the operation so that it is an easy matter toparticularly take into account the necessity of reducing the pollutionof the ambient air to a minimum.

In order to obtain such a minimum pollution of the ambient I air it hasbeen proposed to completely cut off the injection as soon as thepressure in the input manifold of the engine falls below a predeterminedvalue, which low pressure is generally reached when the driver of thevehicle slows down suddenly so that the engine is driven by the vehiclewheels.

In order to still further improve the efficiency of such an arrangementin order to reduce the pollution of the air, it isadvantageous to cutoff the injection, even before the manifold pressure has reached theabove-mentioned predetermined value. The present invention has as itsobject the provision of such an improved arrangement. More specifically,this invention is directed to an electronic control system for fuelinjection in automobile internal combustion engines, wherein a pulsegenerator triggers a flip-flop in synchronism withthe speed of rotationof the engine in order to start the electromagnetically controlledinjection, said flip-flop being returned to its initial condition at theend of a period corresponding to the duration of injection while thespeed of the vehicle and consequently that of the engine are adjusted bythe driver through controlling means acting on the duration ofinjection. According to the invention said control means includes anelectronic connection with said flip-flop for momentarily preventing anyinjection whenever the control means has been shifted at a speed above apredetermined value, whereby the duration of injection is reduced.

According to preferred embodiment of the invention, the control means isconnected with the slider of a voltage-divider fed by a voltage supplywhile a condenser charged transiently by said slider when it has beenshifted is connected with the base of a transistor which is renderedconductive during a predetermined period the length of which depends onthe speed of movement of the slider, on the capacity of the condenserand on the resistances connected in the circuit for charging thecondenser. The collector-emitter circuit of the transistor is connectedin the flip-flop circuit so that it cannot be triggered by the signalsdefining the beginning of the injection as long as said transistor isconductive. The flip-flop is bistable and is triggered by a positivepulse for each injection. The collector of the injection-blockingtransistor is connected with the input of said bistable flip-flopreceiving the positive signals starting the injections and the emitterof said transistor is grounded. Said injection blocking transistor isrendered conductive by a transient positive voltage applied to its basethrough a diode and produced by the firstmentioned condenser connectedwith the slider of the voltage-divider through a resistance, the anodeand cathode of said diode being both grounded through a resistance.

By way of example and in order to further the understanding of thefollowing description, the accompanying drawings is a schematic diagramof the circuit foran electronic injectioncontrol system according to theinvention.

The single FIGURE of said drawing shows that the arrangement accordingto the invention cooperates with a bistable flip-flop and a delaycircuit, which do not form part of the invention, but which will bedescribed hereinafter in order to further the understanding of theoperation of the complete circuit. It should be noted that the improvedarrangement may be used both with a bistable flipflop and with amonostable flipflop.

The bistable flip-flop illustrated includes transistor T 705, of whichthe emitter-collector circuit is connected between the voltage supply Vand ground in series with resistances 706 and 707 and transistor T 710similarly connected with resistances 714a and 714. The bases oftransistor T 705 is connected with the point connecting said resistances714a and 714 through resistance 715 while the base of transistor T 710is connected directly with the point connecting resistances 707 and 706.The base of transistor T 705 is grounded through resistance 854. Theflip-flop is triggered upon application of a positive pulse to the inputE and it is turned off by a negative pulse from the delay circuit. Thedelay circuit comprises unijunction transistor T 805, transistor T 855,diodes 856 and 857, condenser 806 and resistances 802, 802a, 802b. Whenthe flip-flop is triggered condenser 806 is charged with a time constantdepending on its capacity and on the value of the resistance 802. At theend of a predetermined duration the voltage across the tenninals ofcondenser 806 is such that the unijunction transistor T 805 suddenlybecomes conductive and discharges said condenser 806 through theresistances 802a and 802b. Consequently, the voltage applied on the baseof transistor T 855 rises above that applied on its emitter so that saidtransistor T 855 becomes conductive. At this moment the point connectingthe resistances 714a, 714 and 715 is practically at zero voltage whichresults in cutting off transistor T 705 and returning of the bistableflip-flop to its initial state.

The control means according to the invention are adapted to prevent atriggered of the bistable flip-flop during a transient period. Theyinclude transistor T 858 the collector of which is connected with theinput E of the bistable flip-flop while its emitter is directlygrounded.

The base of said transistor T 858 is connected with the slider of apotentiometric voltage-divider 862 through diode 859, condenser 860 andresistance .861. The anode and cathode of the diode 859 are groundedthrough the resistances 863 and 864 respectively. A mechanicalconnection is provided between the slider of the voltage divider 862,connected between the voltage supply VA and ground with the meanscontrolling the duration of injection constituted in the present case bythe accelerator pedal 29. The position of said pedal 29 defines theduration of injection, for instance through a modification of thevoltage applied to the base n2 of the unijunction transistor T 805. Whenthe pedal 29 is shifted in a direction increasing the input of gasthrough the throttle valve, the slider of the voltage divider 862 moves,for example, downwardly whereas the closing of said throttle valveproduces an upward movement of said slider.

As long as said slider remains stationary in any given position thevoltage applied to the base of the transistor T 858 is zero since saidbase is grounded through the resistance 864.

Now, if the driver speedily releases his pedal 29, the slider on thevoltage-divider 862 moves upwardly and consequently a charging currentpasses through condenser 860 which ensures transiently during thecharging of said condenser 860 a saturated condition for the transistorT 858. This results in the base of transistor T 705 being groundedthrough transistor T 858 and therefore transistor T 705 cannot betriggered any more by a pulse applied to the input E, since such a pulseis directly grounded throughout the period of saturation of thetransistor T 858. Consequently, the bistable flip-flop cannot betriggered as long as transistor T 858 is saturated.

Through a suitable selection of the resistance 861 and of the condenser860, it is possible to act on the duration of the transient cutting offof the injection and also on the speed of the shifting of the sliderrequired for the system to become operative.

What I claim is:

1. In an electronically controlled fuel injection system for an internalcombustion engine for driving a vehicle, the engine having a device forsetting the power level of the engine between minimum and maximum powerlevels, the system comprising a pulse generator operatively connectedwith a rotatable shaft of the engine, a switching circuit activated byeach pulse from the pulse generator to produce an injection signal whichis applied to an electro-magnetic fuel injector in cluding amultivibrator circuit which is'released by a pulse applied to an inputthereof, the duration of the injection signal determining the openingduration of the fuel injector and hence the quantity of fuel injected,and control means acting on the switching circuit for varying theduration of the injection signal according to the operating conditionsof the engine, the improvement comprising a means for providing a powersignal in response to any predetermined incremental decrease in thesetting of the engine power level device including a potentiometricvoltage divider, a slider for said voltage divider positioned inresponse to the engine power level device, the predetermined incrementaldecrease being that between any greater and lesser power level settingin the range of power level settings of the device, and

. means connected to the switching circuit and responsive to the powersignal for interrupting the operation of the switching circuit andthereby the fuel injection, including a condenser adapted to have itscharge changed through the slider upon shifting of the latter, aresistance inserted between the condenser and the slider, a transistorthe collector of which is connected with the multivibrator input and theemitter of which is grounded, a diode connecting the condenser with thebase of the transistor, and resistances grounding the terminals of thediode, the transient pulses generated by a rapid shifting of the sliderbeing applied to the base of the transistor, whereby the transistorgrounds the multivibrator and renders it transiently inoperative.

k k I? k

1. In an electronically controlled fuel injection system for an internalcombustion engine for driving a vehicle, the engine having a device forsetting the power level of the engine between minimum and maximum powerlevels, the system comprising a pulse generator operatively connectedwith a rotatable shaft of the engine, a switching circuit activated byeach pulse from the pulse generator to produce an injection signal whichis applied to an electro-magnetic fuel injector including amultivibrator circuit which is released by a pulse applied to an inputthereof, the duration of the injection signal determining the openingduration of the fuel injector and hence the quantity of fuel injected,and control means acting on the switching circuit for varying theduration of the injection signal according to the operating conditionsof the engine, the improvement comprising a. means for providing a powersignal in response to any predetermined incremental decrease in thesetting of the engine power level device including a potentiometricvoltage divider, a slider for said voltage divider positioned inresponse to the engine power level device, the predetermined incrementaldecrease being that between any greater and lesser power level settingin the range of power level settings of the device, and b. meansconnected to the switching circuit and responsive to the power signalfor interrupting the operation of the switching circuit and thereby thefuel injeCtion, including a condenser adapted to have its charge changedthrough the slider upon shifting of the latter, a resistance insertedbetween the condenser and the slider, a transistor the collector ofwhich is connected with the multivibrator input and the emitter of whichis grounded, a diode connecting the condenser with the base of thetransistor, and resistances grounding the terminals of the diode, thetransient pulses generated by a rapid shifting of the slider beingapplied to the base of the transistor, whereby the transistor groundsthe multivibrator and renders it transiently inoperative.